The present invention relates to a key for use in a cylinder lock with a rotatable key plug having a profiled keyway including a longitudinal profile rib at at least one sidewall of the keyway, said key comprising:
an elongated, substantially flat key blade having a longitudinal profile groove extending along at least a portion of the length of the key blade, with a bottom wall of said groove being substantially parallel to a side surface of said flat key blade,
said longitudinal profile groove having an undercut portion adjacent to a ridge portion, the outside of which forms part of a side surface of the key blade and the inside of which comprises a sidewall portion being inclined and facing said bottom wall of said groove.
Such a key with an undercut groove is previously known, e.g. from U.S. Pat. No. 5,715,717 (Widén) or U.S. Pat. No. 5,640,865 (Widén). Such keys have proven to be very useful in that they provide an improved security. The key profile is quite distinguished from conventional keys, and it is rather difficult to copy such keys. Moreover, they permit a great variation of the cross-sectional profile, which is a great advantage.